<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<div style="font-size:14px">em<!-- 14px  -->
  <span style="font-size:1.4em;">em<!-- (14*1.4)px  -->
      <span style="font-size:1.4em;">em<!-- (14*1.4*1.4)px  -->
         <span style="font-size:1.4em;">em<!-- (14*1.4*1.4*1.4)px  -->
            <span style="font-size:1.4em;">em<!-- (14*1.4*1.4*1.4*1.4)px  -->
            </span>
         </span>
      </span>
   </span>
</div>
</body>
</html>
